The present invention relates to a collector ring arrangement as well as to a method of producing the collector ring arrangement.
For supplying and withdrawing current to and from the rotor windings of an electrical machine, a collector ring arrangement is provided on the rotor shaft. Such collector ring arrangements in a prior art are composed of a synthetic plastic body which is pressed outside the bearings or between the bearings on the rotor shaft. The rotor shaft is reduced by a chip removing operation at this location during outer mounting, and the speed during chip removal must be adjusted to the stability which depends on the diameter. The collecting ring arrangement includes collecting rings which are correspondingly connected to the rotor winding through a current rail. Carbon brushes abut against the collecting rings for current transmission.
It is important to maintain the outer diameter of the collecting ring as small as possible. The smaller collecting ring in the outer diameter, the lower the peripheral speed of the grinding ring, and as the result the lower the surface temperature and the lower is the wear of the brushes. For this reason, it is conventional in the prior art to reduce the rotor shaft in a region in which it carries the collecting ring arrangement. It is therefore has been suggested to design the individual components, namely the synthetic plastic body, the current rails and the collector ring as thin as possible in their radial dimensions, to obtain an outer diameter of the total arrangement as small as possible. Such thin components are however to be mounted only with extreme caution, since they can be easily deformed. The reduction of the diameter of the shaft means a material expense for the working tools and the time expense for the reduction process, in particular in the end phase of the process, since with the reduced diameter the working speed because of lacking stability of the shaft must be throttled, or in other words the shaft is time-critical in the manufacture.
For reducing the radial thickness of the collector ring arrangement, it has been proposed in the European Patent Document EP-B 94 163 to produce the synthetic plastic body by injection molding, and during formation of the synthetic plastic body to incorporate the corresponding current rails and the collector ring in the synthetic plastic body. The thusly produced unit of synthetic plastic body and conductive elements is pressed onto the rotor shaft of the machine. The current rails require naturally a certain own rigidity, or in other words material thickness, and the synthetic plastic body must be correspondingly stable for mounting the unit on the shaft.